U.S. patent application number 12/493624 was filed with the patent office on 2010-01-07 for probe-array substrate, probe array, and method of producing the same.
This patent application is currently assigned to Murata Manufacturing Co., Ltd.. Invention is credited to TERUHISA SHIBAHARA.
Application Number | 20100004143 12/493624 |
Document ID | / |
Family ID | 41464828 |
Filed Date | 2010-01-07 |
United States Patent
Application |
20100004143 |
Kind Code |
A1 |
SHIBAHARA; TERUHISA |
January 7, 2010 |
PROBE-ARRAY SUBSTRATE, PROBE ARRAY, AND METHOD OF PRODUCING THE
SAME
Abstract
A probe-array substrate includes a plurality of probe holding
units each having a projection that exhibits a hydrophilicity and a
hydrophobic region disposed so as to surround each of the probe
holding units. The probe-array substrate can further include an
inspection region for use in checking whether mixture of probe
solutions is present among the plurality of probe holding units.
The inspection region is disposed between the neighboring probe
holding units across the hydrophobic region.
Inventors: |
SHIBAHARA; TERUHISA;
(Tokyo-to, JP) |
Correspondence
Address: |
DICKSTEIN SHAPIRO LLP
1633 Broadway
NEW YORK
NY
10019
US
|
Assignee: |
Murata Manufacturing Co.,
Ltd.
Nagaokakyo-shi
JP
|
Family ID: |
41464828 |
Appl. No.: |
12/493624 |
Filed: |
June 29, 2009 |
Current U.S.
Class: |
506/16 ;
506/32 |
Current CPC
Class: |
B01L 2300/161 20130101;
B01J 2219/00722 20130101; B01L 3/0262 20130101; B01J 19/0046
20130101; B01J 2219/00659 20130101; B01L 2400/022 20130101; B01L
2300/0819 20130101; B01J 2219/00619 20130101; B01J 2219/00509
20130101; B01L 3/5088 20130101; B01J 2219/0074 20130101; B01L
2200/0642 20130101; B01J 2219/00527 20130101; B01J 2219/0036
20130101; B01L 2300/0609 20130101; B01J 2219/00725 20130101 |
Class at
Publication: |
506/16 ;
506/32 |
International
Class: |
C40B 40/06 20060101
C40B040/06; C40B 50/18 20060101 C40B050/18 |
Foreign Application Data
Date |
Code |
Application Number |
Jul 7, 2008 |
JP |
2008-178716 |
Claims
1. A probe-array substrate comprising: a main surface; a plurality
of probe holding units each comprising a high wettability region
arranged on the main surface, the high wettability region
exhibiting a relatively high wettability with respect to a probe
solution, as indicated by a contact angle therewith of 90.degree.
or less; and a low wettability region disposed so as to surround
each of the plurality of probe holding units, wherein the low
wettability region exhibits a relatively low wettability with
respect to a probe solution, as indicated by a contact angle
therewith of more than 90.degree..
2. The probe-array substrate according to claim 1, wherein the
region exhibiting a relatively high wettability comprises a
projection.
3. The probe-array substrate according to claim 2, wherein the
projections project from the low wettability region, and the probe
holding units consist of the projections.
4. The probe-array substrate according to claim 2, wherein a probe
holding unit comprises the projection and a high wettability region
disposed around the projection on the main surface.
5. The probe-array substrate according to claim 4, wherein a probe
holding unit is disposed in a recessed section of the main
surface.
6. The probe-array substrate according to claim 5, further
comprising an inspection region exhibiting a relatively high
wettability with respect to each of a number of predetermined probe
solutions, wherein a low wettability region is disposed between the
inspection region and each of neighboring probe holding units of
the plurality of probe holding units.
7. The probe-array substrate according to claim 6, wherein the
projection comprises a guide groove for facilitating an
introduction of a probe solution into the probe holding unit.
8. The probe-array substrate according to claim 7, wherein the
probe solution is an aqueous solution, the main surface is
hydrophilic, and the low wettability region is a cured
photosensitive resin film on the main surface.
9. The probe-array substrate according to claim 8, wherein the
probe holding unit is disposed in a portion of the main surface
from which the resin film is absent.
10. The probe-array substrate according to claim 4, wherein each of
the plurality of probe holding units includes a wall surrounding
the projection, and a resin-coated groove section disposed between
neighboring walls of the walls, wherein the grove section comprises
a low wettability region and a high wettability region on its
surface.
11. The probe-array substrate according to claim 4, further
comprising an inspection region exhibiting a relatively high
wettability with respect to each of a number of predetermined probe
solutions, wherein a low wettability region is disposed between the
inspection region and each of neighboring probe holding units of
the plurality of probe holding units.
12. The probe-array substrate according to claim 3, wherein a probe
holding unit is disposed in a recessed section of the main
surface.
13. The probe-array substrate according to claim 12, further
comprising an inspection region exhibiting a relatively high
wettability with respect to each of a number of predetermined probe
solutions, wherein a low wettability region is disposed between the
inspection region and each of neighboring probe holding units of
the plurality of probe holding units.
14. The probe-array substrate according to claim 2, wherein a probe
holding unit is disposed in a recessed section of the main
surface.
15. The probe-array substrate according to claim 14, further
comprising an inspection region exhibiting a relatively high
wettability with respect to each of a number of predetermined probe
solutions, wherein a low wettability region is disposed between the
inspection region and each of neighboring probe holding units of
the plurality of probe holding units.
16. A probe array comprising: a probe-array substrate according to
claim 1; and a probe molecule in a plurality of probe holding units
of the probe-array substrate.
17. A method of producing a probe array, the method comprising:
providing a probe-array substrate according to claim 1; providing a
supplying unit that has nozzles arranged so as to correspond to the
projections, a plurality of the nozzles having a probe solution
therein; and positioning the nozzles of the supplying unit
sufficiently near to the corresponding projection to cause the
probe solution and the projection to come into contact with each
other, and thus guiding the probe solution into the probe holding
unit.
18. The method of producing a probe array according to claim 17,
wherein I.ltoreq.D/2, where I is a distance from a center of each
of the projections to the low wettability region and D is an outer
diameter of each of the nozzles.
19. The method of producing a probe array according to claim 18,
wherein N>D.times.[arccosh {(2I/D).times.cosh
(.psi.)}-.psi.]/[2.times.cosh (.psi.)]wherein N is the length of
the nozzle, and .psi.=arcsinh (.theta.3), where .theta.3 is a
wetting angle between an outer area of the nozzle and the probe
solution.
20. A method of producing a probe array, the method comprising:
providing a probe-array substrate according to claim 4; providing a
supplying unit that has nozzles arranged so as to correspond to the
projections, each of the nozzles having a probe solution therein;
and bringing the nozzles of the supplying unit sufficiently near to
the corresponding projections to cause the probe solution and the
projection to come into contact with each other, and thus guiding
the probe solution into the probe holding unit, wherein
I<[D.times.cosh {arcsinh (1/tan .theta.2)}]/[2.times.cosh
{arcsinh (tan .theta.3)}], where D is an outer diameter of the
nozzle, I is a distance from a center of the projection to the low
wettability region, .theta.2 is a wetting angle between the high
wettability region adjacent to the probe holding unit in the
probe-array substrate, and .theta.3 is a wetting angle between an
outer area of the nozzle and the probe solution.
21. A method of producing a probe array, the method comprising:
providing a probe-array substrate according to claim 6; providing a
supplying unit that has nozzles arranged so as to correspond to the
projections, each of the nozzles containing a probe solution;
bringing the nozzle of the supplying unit sufficiently near to the
corresponding projection to cause the probe solution and the
projection to come into contact with each other, and thus guiding
the probe solution into the probe holding unit; and separating the
nozzle and probe solution; wherein the sequence of providing and
positioning and separating steps with a new probe-array substrate
in each sequence is repeated until the sequence in which the
inspection region contains neither probe solution or dried probe
solution is complete.
Description
BACKGROUND OF THE INVENTION
[0001] 1. Field of the Invention
[0002] The present invention relates to a probe-array substrate for
use in a chemical or biochemical field, a probe array constructed
using a probe-array substrate, and a method of producing the
same.
[0003] 2. Description of the Related Art
[0004] DNA chips have captured much attention as a tool for
performing a genetic diagnosis for multiple items at a time,
examining the amount of expression of various types of mRNA at a
time, or examining single nucleotide polymorphisms (SNPs) for
multiple items at a time. The DNA chip, also called a DNA
microarray, is a probe array that uses a known DNA causing
hybridization with a target DNA or RNA molecule as a probe and that
includes different types of probes in a plurality of probe holding
units arranged at regular intervals.
[0005] Antigen or antibody chips have captured attention as a tool
for examining the presence or absence of multiple types of antigens
or antibodies at the same time. These chips are a probe array that
utilize the known antigen coupling (binding) to an antibody and
that includes different types of probes in a plurality of probe
holding units arranged at regular intervals.
[0006] One typical method of producing a probe array is a method of
arranging spots on the surface of a substrate by applying a probe
solution (i.e. a solution containing a probe molecule) on the
substrate, such as a slide glass, in dot form (hereinafter referred
to as spotting) and chemically binding probe molecules to the
surface of the board. Known methods include, for example, a method
of discharging a probe solution onto the substrate using an
injection needle, micropipette, or ink jetting and a method of
bringing a probe solution attached on a needle point into contact
with the substrate.
[0007] An exemplary micropipette for use in practicing the
above-described method utilizing spotting is the micropipette used
in densely arranging droplets having small volume for use. One such
micropipette is disclosed in Japanese Unexamined Patent Application
Publication No. 2004-45055. One example of a method of efficiently
arranging droplets supplied from a micropipette on an array
substrate that has a structure preventing contamination of the
droplets is disclosed in Japanese Unexamined Patent Application
Publication No. 2004-4076.
[0008] In spotting, as previously described, it is necessary to
arrange different types of probe solutions on a substrate. If an
injection needle, micropipette, or ink jetting is used in spotting,
it is necessary to change the solution for every one-point
application, and this sacrifices cost or production speed. To
address this, it is desired that different types of probe solutions
be applied in one spotting.
[0009] If droplets of probe solutions in neighboring spots during
spotting come into contact with each other, the droplets are mixed
and the substrate is defective as a probe array. It is desired that
such a defect occurs less often. In addition, when such a defect is
encountered, it is desired to be able to easily and reliably detect
the defective.
SUMMARY OF THE INVENTION
[0010] Accordingly, it is an object of the present invention to
provide a probe-array substrate, a probe array constructed using
the probe-array substrate, and a method of producing the same that
can satisfy the above-described requirements.
[0011] Preferred embodiments of the present invention are first
directed to a probe-array substrate including a main surface and a
plurality of probe holding units arranged along the main surface.
To solve the above-described technical problems, the probe-array
substrate further includes a low wettability region disposed so as
to virtually surround each of the plurality of probe holding units,
the low wettability region exhibiting relatively low wettability
with respect to a probe solution, and the probe holding unit
includes a projection that exhibits relatively high wettability
with respect to the probe solution.
[0012] The terms "relatively high wettability" and "relatively low
wettability" indicate wettability as indicated by the angle between
a free surface of a liquid and a surface of a solid with which the
surface of the liquid is in contact. Relatively high wettability
means angle of contact (wetting angle) is equal to or less than
90.degree. and relatively low wettability means angle of contact
(wetting angle) exceeds 90.degree., respectively. Accordingly, when
the probe solution is an aqueous solution, "relatively high
wettability" generally means hydrophilic, and "relatively low
wettability" means hydrophobic.
[0013] The projection may project from the low wettability region,
and the probe holding unit may be provided by the projection alone.
Preferably, the probe-array substrate may further include a high
wettability region disposed around the projection on the main
surface, the high wettability region exhibiting relatively high
wettability with respect to the probe solution, and the probe
holding unit may be provided by the projection and the high
wettability region.
[0014] The probe holding unit may have a recessed shape from the
main surface.
[0015] The probe-array substrate may further include an inspection
region for use in checking whether a mixture of probe solutions is
present among the plurality of probe holding units, the inspection
region exhibiting relatively high wettability with respect to each
of the probe solutions. The low wettability region may be disposed
between the inspection region and each of neighboring probe holding
units of the plurality of probe holding units.
[0016] The projection may preferably have a guide groove for
facilitating an introduction of the probe solution into the probe
holding unit.
[0017] According to another aspect of the preferred embodiments of
the present invention, a probe-array substrate has no projections.
Each of a plurality of probe holding units is provided by a region
that exhibits relatively high wettability with respect to a probe
solution. The probe-array substrate further includes a low
wettability region disposed so as to virtually surround each of the
plurality of probe holding units, the low wettability region
exhibiting relatively low wettability with respect to a probe
solution and an inspection region for use in checking whether a
mixture of probe solutions is present among the plurality of probe
holding units, the inspection region exhibiting relatively high
wettability with respect to each of the probe solutions. The low
wettability region is disposed between the inspection region and
each of neighboring probe holding units of the plurality of probe
holding units.
[0018] When the probe solution is an aqueous solution, the
relatively high wettability reflects an affinity for water and the
relatively low wettability does not have an affinity for water, the
probe-array substrate may preferably be made of a hydrophilic
material, and the low wettability region may preferably be provided
by a photosensitive resin film formed by patterning on the surface
of the probe-array substrate using photolithography.
[0019] When the probe solution is an aqueous solution, the
probe-array substrate may preferably be made of a hydrophilic
material, and the main surface may preferably include a resin film
formed thereon. The probe holding unit may preferably be disposed
in a portion from which the resin film is removed by plasma ashing
after the formation of the resin film. The low wettability region
may preferably be provided by the resin film remaining after the
removal using plasma ashing.
[0020] Each of the plurality of probe holding units may include a
wall that virtually surrounds the projection. The probe-array
substrate may include a groove section to which a resin is applied,
the groove section being disposed between neighboring walls. The
low wettability region may be provided by the surface of the resin
remaining after plasma ashing performed such that the resin within
the groove section is not eliminated. At least part of the high
wettability region may be provided by a portion from which an
unnecessary segment of the resin is removed by the plasma
ashing.
[0021] The preferred embodiments of the present invention are also
directed to a probe array including a probe-array substrate
according to at least one of the above-described preferred
embodiments of the present invention and a probe molecule retained
in each of the plurality of probe holding units of the probe-array
substrate.
[0022] The preferred embodiments of the present invention are also
directed to a method of producing a probe array using a probe-array
substrate according to at least one of the preferred embodiments of
the present invention.
[0023] The method of producing a probe array according to at least
one of the preferred embodiments of the present invention includes
preparing a probe-array substrate according to at least one of the
preferred embodiments of the present invention, preparing a
supplying unit that has nozzles arranged so as to correspond to the
projections, each of the nozzles being filled with a probe
solution, and bringing the nozzle of the supplying unit near to the
corresponding projection, causing the probe solution and the
projection to come into contact with each other, and thus guiding
the probe solution into the probe holding unit.
[0024] In the above-described method of producing a probe array,
I.ltoreq.D/2 is preferably true, where I is the distance from a
center of each of the projections to the low wettability region and
D is the outer diameter of each of the nozzles.
[0025] Alternatively, in the above-described method of producing a
probe array, N>D.times.[arccosh {(2I/D).times.cosh
(.psi.)}-.psi.]/[2.times.cosh (.psi.)] is preferably be true when
I>D/2, where I is a distance from a center of each of the
projections to the low wettability region, D is the outer diameter
of each of the nozzles, N is the length of the nozzle, and .psi. is
defined by .psi.=arcsinh (tan .theta.3), where .theta.3 is a
wetting angle between an outer area of the nozzle and the probe
solution.
[0026] In performing the method of producing a probe array
according to at least one of the preferred embodiments, when the
probe-array substrate is prepared in which the high wettability
region, which exhibits relatively high wettability with respect to
the probe solution, is formed around the projection on the main
surface and the probe holding unit is provided by the projection
and the high wettability region, it is preferable that
I<[D.times.cosh {arcsinh (1/tan .theta.2)}]/[2.times.cosh
{arcsinh (tan .theta.3)}], where D is the outer diameter of the
nozzle, I is the distance from a center of the projection to the
low wettability region, .theta.2 is a wetting angle between the
high wettability region adjacent to the probe holding unit in the
probe-array substrate and the probe solution, and .theta.3 is a
wetting angle between an outer area of the nozzle and the probe
solution.
[0027] In performing the method of producing a probe array
according to at least one of the preferred embodiments, when the
probe-array substrate in which the inspection portion is formed is
prepared, it is preferable that after the step of guiding the probe
solution into the probe holding unit, the step of determining that
the probe solution is not attached in the inspection region is
preferably performed.
[0028] With the probe-array substrate according to at least one of
the embodiments of the present invention, relatively high
wettability is provided in the probe holding unit, and the low
wettability region, which exhibits relatively low wettability, is
disposed so as to substantially surround each of the probe holding
unit. Therefore, the probe solution can be smoothly introduced in
the probe holding unit, and is reliably prevented by the low
wettability region from wetting and spreading out on the main
surface. Accordingly, the density of probes in a probe array can be
increased.
[0029] When the probe holding unit of the probe-array substrate
according to at least one of the embodiments of the present
invention includes a projection that exhibits relatively high
wettability, the wetting force acting between the probe solution
and the projection enables the introduction of the probe solution
into the probe holding unit more smoothly.
[0030] When the probe-array substrate according to at least one of
the embodiments of the present invention includes the inspection
region, the occurrence of a defect caused by mixture
(cross-contamination) of droplets of neighboring probe solutions
can be reliably detected by, after the probe solution is introduced
into the probe holding unit of the probe-array substrate, checking
whether the inspection region is wet or whether there is an
indication of drying after wetting.
[0031] With the method of producing a probe array according to at
least one of the embodiments of the present invention, many
different types of probe solutions can be supplied from the
supplying unit to the probe-array substrate at a single time.
Therefore, the probe array can be produced efficiently at low cost.
In filling the plurality of nozzles of the supplying unit with the
probe solutions, it is necessary to fill the plurality of nozzles
with different types of the probe solutions. This operation can be
relatively time consuming and costly. However, because the probe
solutions can be supplied to many probe-array substrates using a
supplying unit and the probe solutions once inserted are retained,
the operation is not time consuming and costly.
[0032] With the method of producing a probe array according to at
least one of the embodiments of the present invention, the
projection, which exhibits relatively high wettability, of the
probe holding unit and the nozzle containing the probe solution are
brought near to each other are caused to come into contact with
each other to guide the probe solution into the probe holding unit.
Accordingly, a capillary phenomenon and wetting force acting
between the probe solution and the projection enables the probe
solution to be introduced into the probe holding unit smoothly and
reliably.
[0033] Other features, elements, characteristics and advantages of
the present invention will become more apparent from the following
detailed description of preferred embodiments of the present
invention (with reference to the attached drawings).
BRIEF DESCRIPTION OF THE DRAWINGS
[0034] FIG. 1 is a perspective view that illustrates in part a
probe-array substrate according to a first embodiment of the
present invention;
[0035] FIG. 2 is a top view that illustrates in part the
probe-array substrate shown in FIG. 1;
[0036] FIGS. 3A, 3B, 3C, and 3D are cross-sectional views that
illustrate a process performed to produce the probe-array substrate
shown in FIG. 1;
[0037] FIG. 4 is a cross-sectional view that illustrates a
supplying unit advantageously used in combination with the
probe-array substrate to produce a probe array using the
probe-array substrate;
[0038] FIGS. 5A, 5B, 5C, 5D, 5E, and 5F are end views for
describing a process performed to produce the supplying unit shown
in FIG. 4 and illustrate the supplying unit at a specific end
section;
[0039] FIGS. 6A, 6B, and 6C are cross-sectional views that
illustrate a process performed to produce a probe-array using the
probe-array substrate shown in FIG. 1 and the supplying unit shown
in FIG. 4;
[0040] FIG. 7 is an illustration for use in describing a state in
which a solid cylinder is inserted substantially perpendicular to
the liquid level;
[0041] FIG. 8 is an illustration for use in describing how a probe
aqueous solution guided to a hydrophilic region of a probe holding
unit sufficiently wets and spreads out on the hydrophilic
region;
[0042] FIG. 9 is an illustration for use in describing how probe
aqueous solution that covers the whole area of the hydrophilic
region of the probe holding unit wets up on the outer areas of a
nozzle when the relationship I.ltoreq.D/2 is true;
[0043] FIG. 10 is an illustration for use in describing how probe
aqueous solution that covers the whole area of the hydrophilic
region of the probe holding unit wets up on the outer areas of a
nozzle when the relationship I>D/2 is true;
[0044] FIG. 11 is an illustration for use in describing a second
embodiment of the present invention and corresponds to FIG. 2;
[0045] FIG. 12 is an illustration for use in describing a third
embodiment of the present invention and corresponds to FIG. 1;
and
[0046] FIG. 13 is an illustration for use in describing a fourth
embodiment of the present invention and corresponds to FIG. 1.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0047] FIG. 1 illustrates in part of a probe-array substrate 100
according to a first embodiment of the present invention in
perspective view. FIG. 2 is a top view of a part of the probe-array
substrate 100 shown in FIG. 1.
[0048] Referring to FIGS. 1 and 2, the probe-array substrate 100
includes a main surface 101 and is substantially planar as a whole.
A plurality of probe holding units 102 are arranged in a matrix on
the probe-array substrate 100.
[0049] Each of the probe holding units 102 includes a hydrophilic
projection 103. The terms "hydrophilic" and "hydrophobic" are
usually used as terms indicating the presence or absence of
wettability (affinity) for water. In the following description,
however, regardless of whether a probe solution is an aqueous
solution, when wettability for a probe solution is high, the state
is represented as "hydrophilic," and when wettability therefor is
low, the state is represented as "hydrophobic."
[0050] Each of the probe holding units 102 is surrounded by a
hydrophobic region 104 on the main surface 101 of the probe-array
substrate 100. In the present embodiment, a hydrophilic region 105
having a substantially square shape is disposed around the
hydrophilic projection 103 on the main surface 101. Accordingly,
the probe holding unit 102 is provided by the above-described
projection 103 and the hydrophilic region 105. Therefore, a
sufficient amount of a probe solution can be held in each of the
probe holding units 102, and this leads to a reduction in
unevenness of the amounts of probe solutions held in the probe
holding units 102.
[0051] In addition, a hydrophilic inspection region 106 for use in
checking whether mixture (cross-contamination) of probe solutions
is present is disposed on the main surface 101 of the probe-array
substrate 100. The inspection region 106 is disposed between
neighboring probe holding units 102. The hydrophobic region 104
disposed between the inspection region 106 and each of the probe
holding units 102. The inspection region 106 can have a grid shape,
for example. After probe solutions are introduced into the probe
holding units 102, it can be determined whether the inspection
region 106 is wet or whether there is an indication of being dried
after being wet. Therefore, the occurrence of a defect caused by
cross-contamination of droplets of neighboring probe solutions can
be reliably detected with the use of the inspection region 106.
[0052] The above-described projection 103 has a shape in which two
substantially square poles are arranged in a diagonal direction
such that a single edge line of one of the two substantially square
poles is in contact with a single edge line of the other. As
illustrated in FIG. 2, the length of the side of the substantially
square defining a cross section of each of the substantially square
poles can be approximately 5 .mu.m, for example. The distance
between the projection 103 and the hydrophobic region 104 can be
approximately 10 .mu.m, for example. The width of the inspection
region 106 can be approximately 10 .mu.m, for example. In addition,
the height of the projection 103 can be approximately 100 .mu.m,
for example. The arrangement pitch of the neighboring projections
103 can be approximately 60 .mu.m, for example.
[0053] In the projection 103 having the above-described shape, a
guide groove 109 defined by surfaces 107 and 108 and a guide groove
112 defined by surfaces 110 and 111 are opposed to each other in a
diagonal line direction. Each of the guide grooves 109 and 112 has
a substantially L-shaped cross section. The functions of each of
the projection 103 and the guide grooves 109 and 112 will be
described later.
[0054] A method for producing the probe-array substrate 100 is
described, next. FIGS. 3A to 3D illustrate a typical process
performed to produce the probe-array substrate 100.
[0055] First, as illustrated in FIG. 3A, a material board 120 to
become the probe-array substrate 100 is prepared. The material
board 120 can be formed from a monocrystalline silicon substrate
having a thickness of approximately 500 .mu.m, for example.
[0056] Then, as illustrated in the same FIG. 3A, a resist pattern
121 is formed on the surface of the material board 120 using
photolithography. When the resist pattern 121 is described with
reference to the probe-array substrate 100 illustrated in FIG. 2,
the resist pattern 121 is formed so as to cover the portion to
become the projection 103.
[0057] Then, as illustrated in FIG. 3(B), the material board 120 is
dry-etched with a depth of, for example, approximately 100 .mu.m
while the resist pattern 121 is used as a mask. For the
dry-etching, the inductively coupled plasma reactive ion etching
(ICP-RIE) technology is advantageously applied, and etching using a
gas plasma containing atoms of fluorine, such as carbon
tetrafluoride, or sulfur hexafluoride is performed. Upon the
completion of this step, the shape of the projection 103 is
provided to the material board 120.
[0058] Then, as illustrated in FIG. 3C, the resist pattern 121 and
organic contaminants on the surface are removed by cleaning using a
mixed solution of sulfuric acid and hydrogen peroxide.
[0059] Then, as illustrated in FIG. 3D, a photosensitive resin film
122 patterned so as to provide the previously described hydrophobic
region 104 is formed. In FIG. 3D, the thickness of the
photosensitive resin film 122 is exaggerated. A process performed
to form the patterned photosensitive resin film 122 is described
below.
[0060] First, after the structure illustrated in FIG. 3C is
acquired, a photosensitive resin (e.g., photosensitive polyimide)
is applied over the entire surface of that structure.
[0061] Then, ultraviolet irradiation is performed by, for example,
a stepper using an appropriate photomask. When the negative
photosensitive resin is used, the photomask has a pattern that
shields the portions to become the projection 103, the hydrophilic
region 105, and the inspection region 106 from light and that
allows light to reach the portion to become the hydrophobic region
104.
[0062] When development is performed after the ultraviolet
irradiation, the photosensitive resin is patterned, and as
illustrated in FIG. 3D, the photosensitive resin film 122 to
provide the hydrophobic region 104 is formed.
[0063] After that, plasma ashing is performed such that the
photosensitive resin film 122 is not eliminated. This removes resin
slightly attached to a portion at which the photosensitive resin
film 122 should not remain (e.g., a portion to become the
projection 103, the hydrophilic region 105, or the inspection
region 106). When the material board 120 is made of silicon, as
described above, because oxygen plasma is used in plasma ashing,
the uppermost surface of silicon is oxidized. This leads to
satisfactory hydrophilicity in the projection 103, the hydrophilic
region 105, and the inspection region 106.
[0064] In such a way, the probe-array substrate 100 is
acquired.
[0065] The hydrophobic region 104 may not be provided by the
photosensitive resin film 122 formed by patterning using
photolithography, as described above, but may be provided by a
simple resin film. In this case, the projection 103 and the
hydrophilic region 105, which are to become the probe holding unit
102, and the inspection region 106 may be exposed by removal of the
simple resin film by plasma ashing.
[0066] With the above-described method of producing the probe-array
substrate 100, the projection 103 is formed by dry-etching of the
material board 120 made of monocrystalline silicon. The use of this
method enables the fine and high-aspect projection 103 to be
produced by performing an etching process once. The term
"high-aspect" indicates that the depth of etching is larger than
the width of the opening. It is possible for dry-etching of the
material board 120 made of monocrystalline silicon to achieve
processing with an aspect ratio of no less than 20. As an
alternative to such a method using dry-etching, a method using
wet-etching, which is less expensive, may also be used.
[0067] In producing a probe array constructed using the
above-described probe-array substrate 100, more specifically, a DNA
chip in which different types of probe DNAs are arranged, a
supplying unit 200 illustrated in FIG. 4 is used.
[0068] The supplying unit 200 includes a glass portion 202 and a
finely patterned silicon portion 203. The glass portion 202 has a
plurality of through-holes 201 formed with a pitch of, for example,
approximately 240 .mu.m and has a thickness of, for example,
approximately 400 .mu.m. The silicon portion 203 has a nozzle 204
linking with each of the through-holes 201 formed in the glass
portion 202. The inner diameter of the nozzle 204 can be
approximately 30 .mu.m, for example. The thickness of the nozzle
204 can be approximately 10 .mu.m, for example. The outer diameter
of the nozzle 204 can be approximately 50 .mu.m, for example. The
length of the nozzle 204 can be approximately 150 .mu.m, for
example.
[0069] One example method of producing the supplying unit 200 is
described next with reference to FIGS. 5A, 5B, 5C, 5D, 5E, and 5F,
which are end views of the supplying unit 200 at a specific end
section. First, prepared is a 400 .mu.m thick glass wafer, for
example, which has planar polished surfaces at both sides. A resist
pattern mask in applied by photolithography. Through-holes 201 are
made by sandblasting to obtain the glass portion 202 for supplying
unit as illustrated in FIG. 5A. Alternatively, first performing
processing to a depth that exceeds half the overall depth of the
hole from one surface of the glass wafer and then performing
processing from an opposite surface may result in each of the
through-holes 201.
[0070] As illustrated in FIG. 5B, a resist pattern 212 is formed by
photolithography on a first main surface of a silicon wafer 211
that has a thickness of, for example, approximately 350 .mu.m and
that has both surfaces subjected to planar polishing. The silicon
wafer 211 is etched by ICP-RIE while the resist pattern 212 is used
as a mask to recess it by a depth of the order of, for example,
approximately 150 .mu.m. This produces part of the nozzle 204 in
the silicon portion 203.
[0071] Then, as illustrated in FIG. 5C, the resist pattern 212
formed on the silicon wafer 211 is removed using a mixed solution
of sulfuric acid and hydrogen peroxide, and a resist pattern 213 is
formed in a similar way to that for the resist pattern 212 on a
second main surface opposite to the first main surface on which the
resist pattern 212 was formed.
[0072] Then, as illustrated in FIG. 5D, the silicon wafer 211 is
etched by ICP-RIE while the resist pattern 213 is used as a mask,
so that the nozzle 204 extends through the silicon wafer 211.
[0073] Then, as illustrated in FIG. 5E, the resist pattern 213
formed on the silicon wafer 211 is removed using a mixed solution
of sulfuric acid and hydrogen peroxide. This produces the silicon
portion 203 for the supplying unit 200.
[0074] Then, as illustrated in FIG. 5F, in a state where the nozzle
204 of the silicon portion 203 and the through-hole 201 of the
glass portion 202 are aligned, the silicon portion 203 and the
glass portion 202 are bonded by anodic bonding. Anodic bonding is a
technique for bonding silicon and glass by stacking silicon and
glass, heating the stack to the order of approximately 300.degree.
C. to 500.degree. C., and applying a direct-current voltage of
several hundred volts in which silicon is the anode and glass is
the cathode. The performance of anodic bonding couples atoms at the
uppermost surface of silicon and atoms at the uppermost surface of
glass and enables airtight bonding.
[0075] In such a way, the supplying unit 200 can be produced.
[0076] A method of producing a probe array using the
above-described supplying unit 200, more specifically, a method of
producing a DNA chip in which different types of probe DNA are
arranged is described next.
[0077] In the case where the probe-array substrate 100 is
constructed using silicon, a silicon oxide film is formed on the
portions where silicon is exposed in the probe-array substrate 100,
that is, the probe holding unit 102, which is composed of the
projection 103 and the hydrophilic region 105, and the inspection
region 106. By application of an aminosilane to the silicon oxide
film, an amino group is introduced into the silicon surface. After
that, by application of a reagent containing
N-(6-maleimidocaproyloxy)succinimide, the amino group at the
uppermost surface of the probe-array substrate 100 is substituted
with a maleimide group.
[0078] The supplying unit 200 is prepared, and each of the
through-holes 201 in the supplying unit 200 are filled with a probe
aqueous solution 210, as illustrated in FIG. 6A. In this filling, a
micropipette or ink jetting is used. Different types of the probe
aqueous solutions 210 are prepared and are inserted in the
different through-holes 201. As a probe DNA contained in each of
the probe aqueous solutions 210, one in which a thiol group is
added to the 5'-terminus is used in this embodiment. Because the
inner diameter of each of the through-hole 201 and the silicon
portion 203 is sufficient small, the probe aqueous solution 210 in
each of the through-holes 201 quickly reaches the tip of the nozzle
204 by capillary action, and the surface tension prevents the probe
aqueous solution 210 from spontaneously flowing out of the nozzle
204.
[0079] To prevent the probe DNA from being attracted to the surface
of the supplying unit 200 and the density of the probe aqueous
solution 210 from decreasing, the supplying unit 200 may be rinsed
with the probe aqueous solution 210 one or more times.
Alternatively, before the probe aqueous solution 210 is inserted
into each of the through-holes 201, the supplying unit 200 may be
washed with an aqueous solution of bovine serum albumin (BSA) or an
appropriate DNA fragment to block the surface of the supplying unit
200.
[0080] Then, the probe-array substrate 100 and the supplying unit
200 placed in proper alignment are brought nearer to each other. As
a result, each of the probe aqueous solutions 210 positioned in the
openings of the nozzles 204 comes into contact with the projection
103 on the probe-array substrate 100. At this time, as one example,
when the tip of the nozzle 204 and the main surface 101 of the
probe-array substrate 100 are brought nearer such that the distance
therebetween is the order of approximately 80 .mu.m, the projection
103 has been inserted into the nozzle 204 by approximately 20
.mu.m, so the probe aqueous solution 210 and the projection 103 are
in contact with each other with reliability.
[0081] When the probe aqueous solution 210 and the projection 103
come into contact with each other, as described above, the wetting
force acting between the probe aqueous solution and the probe
holding unit 102 of the probe-array substrate 100 causes the probe
aqueous solution 210 to wet the projection 103 and spread out on
the hydrophilic region until the probe aqueous solution 210 is
stopped by the hydrophobic region 104. In such a way, as
illustrated in FIG. 6B, the probe aqueous solution 210 is
introduced in each of the probe holding unit 102. The detailed
mechanism of action will be described later.
[0082] Then, when the supplying unit 200 is separated from the
probe-array substrate 100 after a predetermined period of time
elapses, as illustrated in FIG. 6C, a state is obtained in which
the probe aqueous solution 210 is attached to the probe holding
unit 102, which includes the projection 103, of the probe-array
substrate 100.
[0083] When the projections 103 are disposed with a pitch of
approximately 60 .mu.m on the probe-array substrate 100 and the
nozzles 204 are disposed with a pitch of approximately 240 .mu.m in
the supplying unit 200, the probe aqueous solution 210 cannot be
attached to some of the probe holding units 102 of the probe-array
substrate 100. However, if four supplying units 200 having
different types of the probe aqueous solutions 210 therein are
prepared and the probe aqueous solutions 210 are sequentially
introduced to the probe-array substrate 100, the different probe
aqueous solutions 210 can be provided to all of the probe holding
units 102.
[0084] When the probe aqueous solution 210 attached to each of the
probe holding units 102 of the probe-array substrate 100 is set
aside for a certain period of time, the maleimide group coupled to
the silicon surface exposed to the probe holding unit 102 and the
thiol group introduced in probe DNA molecules are chemically bound
to each other. As a result, a state is obtained in which probe DNA
molecules to become a probe are retained in the probe holding unit
102 of the probe-array substrate 100.
[0085] When the probe holding unit is rinsed with water and dried
it, the DNA chip is completed.
[0086] In the above embodiment, binding of the maleimide group and
thiol group is used in binding of probe DNA molecules and the
probe-array substrate 100. However, other types of binding, such as
avidin-biotin binding, may also be used.
[0087] The probe DNA aqueous solution may be attached to the
probe-array substrate 100 using a simple nozzle (capillary tube)
without use of the supplying unit 200. However, with this method,
the nozzle must be aligned and brought into close position each
time for all the probe holding units 102 on the probe-array
substrate 100, so it is time consuming and costly. Therefore, as
illustrated in FIGS. 6A to 6C, it may be preferable that the
supplying unit 200 having a plurality of nozzles be used.
[0088] In filling a plurality of nozzles 204 of the supplying unit
200 with different probe aqueous solutions 210, it is necessary to
fill the plurality of nozzles 204 with the different types of the
probe aqueous solutions 210. This operation can be relatively time
consuming and costly. However, because the probe aqueous solutions
210 can be supplied to many probe-array substrates 100 using the
supplying unit 200 retaining the probe aqueous solutions 210 once
inserted, in terms of a single probe array, the operation is not
time consuming and costly.
[0089] In a step of transferring the probe aqueous solution 210 to
the probe-array substrate 100 illustrated in FIG. 6B, if a probe
aqueous solution 210 reaches an adjacent probe holding unit 102,
mixture (cross-contamination) of probe aqueous solutions 210 occurs
between the probe holding units 102. This causes binding of
unintended types of probe DNA molecules, and the resulting DNA chip
is defective. Accordingly, it is necessary to identify such a
defect with reliability.
[0090] With the present embodiment, if a probe aqueous solution 210
reaches an adjacent probe holding unit 102, the probe aqueous
solution 210 also inevitably reaches the inspection region 106.
Accordingly, if it can be confirmed that the probe aqueous solution
210 has not reached the inspection region 106, it can be determined
that an above-described defect resulting from cross-contamination
has not occurred. Therefore, immediately after the step illustrated
in FIG. 6B or immediately after the step illustrated in FIG. 6C, a
defect resulting from cross-contamination can be detected by
checking whether the inspection region 106 is wet or not.
Alternatively, a defect resulting from cross-contamination may also
be detected by checking whether there is an indication of drying
after the probe aqueous solution 210 is once attached (e.g., salt
residue) when the steps illustrated in FIGS. 6B and 6C are
completed and a subsequent step is completed.
[0091] With the method illustrated in FIGS. 6A to 6C, the wetting
force acting between the probe holding unit 102 of the probe-array
substrate 100 and the probe aqueous solution 210 causes the probe
aqueous solution 210 to be introduced and filled into the probe
holding unit 102 of the probe-array substrate 100. Its mechanism of
action is described below with reference to FIGS. 7 to 10.
[0092] FIG. 7 illustrates a state in which a solid cylinder 401 is
inserted to the surface of a liquid 400 in the direction
substantially perpendicular to the liquid surface. In FIG. 7, the
x-axis is set along the central axis of the cylinder 401. When
cross-sections are taken at every x coordinate, each of the
surfaces of the liquid 400 has a substantially circular shape whose
center is the x-axis.
[0093] When the radius of the circle is y, the surface area S of
the surface of the liquid 400 can be represented by Equation 1
below.
x ( 2 .pi. y y ' y ' 2 + 1 ) = 2 .pi. y ' 2 + 1 1 + y ' 2 - y y ' =
0. ( 3 ) ##EQU00001##
[0094] The action of the surface tension makes the surface area of
the liquid 400 a minimum. Liquid 400 has its source of supply, so
there is no limitation to maintain the volume of the liquid 400
constant. Accordingly, the definite integral of expression 1 is at
a stationary value with respect to a minute change in the function
form of y. Hence, the differential equation is expressed by
Equation 2 below (see pp. 13-20 of Akira Harashima, RIKIGAKU
II-Analytical Dynamics, Shokabo, 21st Edition, Oct. 25, 1990).
S = .intg. x 1 x 2 2 .pi. y ( x ) 2 + ( y ) 2 = .intg. x 1 x 2 2
.pi. y y ' 2 + 1 x ( 1 ) ##EQU00002##
[0095] When Equation 2 is rearranged, the following Equation 3 is
obtained.
x y , ( 2 .pi. y y ' 2 + 1 ) = y ( 2 .pi. y y ' 2 + 1 ) ( 2 )
##EQU00003##
[0096] Then, when the differential equation of Equation 3 is
solved, the following Equation 4 is derived.
y=Acosh {(x-B)/A} (4)
[0097] In Equation 4, A and B are constant values determined
depending on the boundary conditions. For example, in the case of
FIG. 7, the boundary condition is that the angle .theta. between
the cylinder 401 and the liquid 400 is a natural wetting angle.
Cosh is a hyperbolic cosine function and is defined by the
following Equation 5.
Cosh.xi.={exp .xi.+exp (-.xi.)}/2 (5)
[0098] In the case where the method illustrated in FIGS. 6A to 6C
is used and the projection 103 of the probe holding unit 102 in the
probe-array substrate 100 and the probe aqueous solution 210 are in
contact with each other, as in the first physical step, the probe
aqueous solution 210 is guided by the projection 103 to the
hydrophilic region 105 of the probe holding unit 102. Because
projection 103 is hydrophilic, the probe aqueous solution 210 moves
on the guide grooves 109 and 112 (see FIG. 2) of the projection 103
and is guided to the hydrophilic region 105 by capillary
action.
[0099] Even when the projection 103 has no guide groove, if the
projection 103 is inserted deep into the opening of the nozzle 204
included in the silicon portion 203 of the supplying unit 200 and
the tip of the silicon portion 203 and the hydrophilic region 105
of the probe holding unit 102 are brought sufficiently near to each
other, the probe aqueous solution 210 reaches the hydrophilic
region 105 of the probe holding unit 102. Accordingly, projection
103 need not necessarily have a guide groove. However, to
facilitate guiding of the probe aqueous solution 210 to the
hydrophilic region 105 of the probe holding unit 102 more reliably
and smoothly, it is preferable that the projection 103 have a guide
groove.
[0100] When the projection 103 guides the probe aqueous solution
210 to the hydrophilic region 105 of the probe holding unit 102, as
described above, as the next step, it is preferable that the probe
aqueous solution 210 sufficiently wet and spread out on the
hydrophilic region 105 of the probe holding unit 102 and reach the
inner edge of the hydrophobic region 104. The condition for
carrying out this step is described below using FIG. 8.
[0101] In practice, the probe holding unit 102 has a finite size
and is defined by the inner edge of the hydrophobic region 104. In
the following discussion, a state is assumed where the probe
holding unit 102 is large infinitely and the hydrophobic region 104
does not exist. Under these conditions, when the wetting spread
amount Rw exceeds the hydrophilic region 105, in theory, the probe
aqueous solution 210 covers the entire area of the hydrophilic
region 105.
[0102] Also, Equation 4 described above is true between the radius
y of the probe aqueous solution 210 in FIG. 8 and x. For the "tip
of wetting" in the hydrophilic region 105 of the probe holding unit
102, the angle between the probe holding unit 102 and the probe
aqueous solution 210 is a natural wetting angle .theta.2. For the
"tip of wetting" on the outer surface of the nozzle 204, the angle
between the outer surface of the nozzle 204 and the probe aqueous
solution 210 is a natural wetting angle .theta.3. From these, when
the wetting spread amount Rw of the probe aqueous solution 210 is
calculated, the following Equation 6 is obtained.
Rw=[D.times.cosh {arcsinh (1/tan .theta.2)}]/[2.times.cosh {arcsinh
(tan .theta.3)}] (6)
where D is the outer diameter of the nozzle 204 of the supplying
unit 200. Accordingly, when the distance from the center of the
projection 103 to the hydrophobic region 104 is I and the following
Equation 7 is true, it can be said that the probe aqueous solution
210 covers the entire area of the hydrophilic region 105 of the
probe holding unit 102.
I<[D.times.cosh {arcsinh (1/tan .theta.2)}]/[2.times.cosh
{arcsinh (tan .theta.3)}] (7)
[0103] In practice, the probe aqueous solution 210 may wet and
spread out more than the above calculation in such a way that the
probe aqueous solution 210 moves into recesses of microscopic
asperities of the hydrophilic region 105 of the probe holding unit
102. Accordingly, it is not necessarily said that if Equation 7 is
not true, the probe aqueous solution 210 always does not cover some
parts of the hydrophilic region 105. However, to reliably cover the
entire area of the hydrophilic region 105 with the probe aqueous
solution 210, it is preferable that Equation 7 be true.
[0104] Referring to the above-described example, the distance I
from the center of the projection 103 to the hydrophobic region 104
is approximately 15 .mu.m, the outer diameter D of the nozzle 204
of the supplying unit 200 is approximately 50 .mu.m, and the
wetting angles .theta.2 and .theta.3 between the silicon oxide film
and water are approximately 4.degree. to 20.degree.. Although each
of the wetting angles .theta.2 and .theta.3 has a value that varies
depending on the cleanliness of the surface, the above range is
general value of possible angles between the silicon oxide film and
water.
[0105] The left-hand and right-hand sides of Equation 7 are
calculated using the above values. The left-hand side is
approximately 15 .mu.m. Although varying depending on the values of
.theta.2 and .theta.3, when considered in the range of
approximately 4.degree. to 20.degree., the right-hand side has a
minimum value of approximately 68 .mu.m at
.theta.2=.theta.3=4.degree. and has a maximum value of
approximately 357 .mu.m at .theta.2=.theta.3=20.degree..
Accordingly, Equation 7 is true in either case. Hence, with the
above-described specific example, the probe aqueous solution 210
can reliably cover the entire area of the hydrophilic region 105 of
the probe holding unit 102.
[0106] When the length of the nozzle 204 in the silicon portion 203
of the supplying unit 200 is not sufficient, the probe aqueous
solution 210 wetting the outer area of the nozzle 204 may reach the
downward surface of the supplying unit 200 and the probe aqueous
solutions 210 in the neighboring nozzles 204 may be mixed. To avoid
mixture of the different probe aqueous solutions 210, it is
necessary for each of the nozzles 204 to have a sufficiently long
length. A preferable length of the nozzle 204 is discussed
below.
[0107] First, as illustrated in FIG. 9, when the outer diameter of
the nozzle 204 is D and the distance from the center of the
projection 103 to the hydrophobic region 104 is I, if I.ltoreq.D/2,
the probe aqueous solution 210 does not wet up on the outer area of
the nozzle 204 regardless of the length N of the nozzle 204.
[0108] As illustrated in FIG. 10, if I>D/2, to find a preferable
length of the nozzle 204, calculation of the wetting amount Nw
illustrated in FIG. 10 is sufficient. Also in FIG. 10, between the
radius y of the probe aqueous solution 210 and x, the
above-described Equation 4 is true. At the "tip of wetting" on the
outer area of the nozzle 204, the angle between the outer area of
the nozzle 204 and the probe aqueous solution 210 is the natural
wetting angle .theta.3. From these, when the wetting amount Nw is
calculated, the following Equation 8 is obtained.
Nw=D.times.[arccosh {(2I/D).times.cos h
(.psi.)}-.psi.]/[2.times.cos h (.psi.)] (8)
[0109] Here, .psi. is defined by the following Equation 3 using
.theta.3.
.psi.=arcsinh (tan .theta.3) (9)
[0110] When the length of the nozzle 204 is N, N is longer than
above-calculated Nw and the following Equation 10 is true, the
wetting of the probe aqueous solution 210 can be stopped before the
top of the nozzle 204.
N>D.times.[arccosh {(2I/D).times.cosh
(.psi.)}-.psi.]/[2.times.cosh (.psi.)] (10)
[0111] Referring to the above-described specific example, the
length N of the nozzle 204 is approximately 150 .mu.m, the outer
diameter D of the nozzle 204 is approximately 50 .mu.m, the
distance I from the center of the projection 103 to the hydrophobic
region 104 is approximately 15 .mu.m, and the wetting angle
.theta.3 between the silicon oxide film is in the range of
approximately 4.degree. to 20.degree.. It is determined using these
values whether Equation 10 is true.
[0112] First, the left-hand side of Equation 10 is approximately
150 .mu.m. Although varying depending on the value of .theta.3,
when .theta.3 is considered in the range of approximately 4.degree.
to 20.degree., the right-hand side has a maximum value of
approximately 28 .mu.m at .theta.3=4.degree. and has a minimum
value of approximately 21 .mu.m at .theta.3=20.degree..
Accordingly, Equation 10 is true in either case. Hence, with the
above-described specific example, the wetting of the probe aqueous
solution 210 on the outer area of the nozzle 204 stops before the
top of the nozzle 204. Thus, the possibility that the probe aqueous
solution 210 wets the downward surface of the supplying unit 200
and the different probe aqueous solutions 210 are mixed is
reduced.
[0113] The function "arccos h" is contained in Equations 9 and 10.
This is the inverse function of the hyperbolic cosine function "cos
h" defined in Equation 5. In theory, there are two inverse
functions of the hyperbolic cosine function "cosh." However, the
inverse function defined by "arccosh" is a function that always
takes zero or more as the function value. From the above
definition, "arccosh" is uniquely determined.
[0114] When a supplying unit in which a plurality of nozzles are
arranged, such as the illustrated supplying unit 200, is used, it
is preferable that the wetting of the probe aqueous solution on the
downward surface of the supplying unit be avoided because that
wetting causes mixture of different probe aqueous solutions, and
accordingly, it is preferable that Equation 10 be true. Even if a
single nozzle is used, it is undesirable that the probe aqueous
solution wet the part to be caught and operated be avoided.
Therefore, it is preferable that Equation 10 be true and the length
of the nozzle be sufficiently long with respect to the wetting
amount of the probe aqueous solution.
[0115] If the outer area of the nozzle is hydrophobic, this is
preferable in that the wetting by the probe aqueous solution is
reduced. At this time, it is not necessary for the nozzle to be
hydrophobic at the entire outer area. The advantage of reducing
excessive wetting is obtainable as long as the tip and its adjacent
area of the nozzle remain hydrophilic and at least base and its
adjacent area of the nozzle are hydrophobic. One example of a
method for making the outer area of the nozzle hydrophobic is a
method of applying hydrophobic liquid.
[0116] FIG. 11 is an illustration for use in describing a second
embodiment of the present invention and corresponds to FIG. 2. In
FIG. 11, similar reference numerals are used in the elements
corresponding to those illustrated in FIG. 2, and the redundant
description is omitted.
[0117] In a probe-array substrate 100a illustrated in FIG. 11, the
hydrophilic region 105 forming a portion of the probe holding unit
102 and the inspection region 106 are coupled with a hydrophilic
region 114 having a narrow width. The narrow hydrophilic region 114
is disposed therebetween and extends across the hydrophobic region
104. Even in this embodiment, if the width of the narrow
hydrophilic region 114 is sufficiently small, a probe solution
properly introduced in the probe holding unit 102 does not flow
into the inspection region 106 through the narrow hydrophilic
region 114. This is because when the probe solution is moving in
the narrow hydrophilic region 114, if the width of the narrow
hydrophilic region 114 is sufficiently narrow, the sum of an
increase in surface free energy caused by the wetting in the
hydrophobic region 104 at both sides of the narrow hydrophilic
region 114 and an increase in surface-tension free energy caused by
an increase in the surface area of the probe solution is larger
than a decrease in surface free energy caused by the wetting on the
surface of the narrow hydrophilic region 114.
[0118] The narrow hydrophilic region 114 does not offer a
particularly advantageous operation and effect. However, the second
embodiment has significance in confirming that the probe-array
substrate including the narrow hydrophilic region 114 is within the
scope of the present invention.
[0119] FIG. 12 is an illustration for use in describing a third
embodiment of the present invention and corresponds to FIG. 1. In
FIG. 12, the same or similar reference numerals are used in the
elements corresponding to those illustrated in FIG. 1, and the
redundant description is omitted.
[0120] In a probe-array substrate 100b illustrated in FIG. 12, the
probe holding unit 102 is provided by the projection 103 alone.
Accordingly, the hydrophobic region 104 is the portion other than
the portion where the projection 103 on the main surface 101 of the
probe-array substrate 100b. The projection 103 projects from the
hydrophobic region 104.
[0121] To produce the probe-array substrate 100b through the steps
illustrated in FIGS. 3A to 3C described above, after the projection
103 is formed on the material board 120, liquid resin is applied on
the material board, a resin film is formed by spin coating, and
then the resin film is cured. At this time, the thickness of the
resin film formed on the top surface and the side surface of the
projection 103 is smaller than the thickness of the resin film
formed on the portion other than the projection 103. After that,
the resin film formed on the top surface and the side surface of
the projection 103 is substantially completely removed, and if
plasma ashing is performed under the condition such that the resin
film formed on the portion other than the projection 103 is not
eliminated, the target probe-array substrate 100b is obtained.
[0122] With the above-described production method, the resin film
to become the hydrophobic region 104 can be formed without use of
photolithography. Accordingly, a lower cost production can be
achieved, in comparison with the production of the previously
described probe-array substrate 100. In addition, because the resin
used is not necessarily photosensitive, the scope of selection of
resin can be enhanced.
[0123] FIG. 13 is an illustration for use in describing a fourth
embodiment of the present invention and corresponds to FIG. 1. In
FIG. 13, the same or similar reference numerals are used in the
elements corresponding to those illustrated in FIG. 1, and the
redundant description is omitted.
[0124] For a probe-array substrate 100c illustrated in FIG. 13, a
wall 116 is disposed so as to surround the projection 103 in each
of the plurality of probe holding units 102. The height of the wall
116 is substantially the same as that of the projection 103. The
groove section between the neighboring walls 116 is filled with a
resin 117. The hydrophobic region 104 is provided by the surface of
the resin 117 filled into the groove section. The inspection region
106 is provided by the top surface of a protrusive wall 118. The
protrusive wall 118 forms an island at the groove section between
the neighboring walls 116.
[0125] To produce the probe-array substrate 100c through the steps
similar to those illustrated in FIGS. 3A to 3C described above, the
projection 103, the wall 116, and the protrusive wall 118 are
simultaneously formed. A liquid resin is poured between the
neighboring walls 116, and the liquid resin is cured. Then, the
resin attached on the portion other than the groove section between
the neighboring walls 116 and on the top surface of the protrusive
wall 118 is removed by, for example, plasma ashing performed such
that the resin 117 filled between the neighboring walls 116 is not
eliminated. When the material board to which such processing is to
be performed is made of silicon, the above-described plasma ashing
produces an oxide film on its uppermost surface.
[0126] When the above-described probe-array substrate 100c is used,
a larger amount of probe solution can be retained in the probe
holding unit 102 in comparison with when the previously described
probe-array substrate 100 is used because the probe holding unit
102 is provided with a recessed shape. Because a relatively large
amount of probe solution can be spotted, it is easy to control the
amount of the probe solution to be spotted, and it is easy to
reduce unevenness of the amount of the probe solution spotted.
[0127] When the above-described probe-array substrate 100c is used,
the wall 116 can block the probe solution from spreading even if a
slightly excessive amount of a probe solution is spotted.
Accordingly, the amount of the probe solution to be spotted can be
set larger. This also contributes to facilitation of control on the
amount of the probe solution to be spotted and reduction in
unevenness of the probe solution spotted.
[0128] In addition, when the above-described probe-array substrate
100c is used, probe molecules can be retained on its side surface
because the probe holding unit 102 is provided by a recessed shape.
Accordingly, the number of probe molecules retainable in the probe
holding unit 102, i.e., the number of probe molecules retained in a
spot, can be increased, so the sensitivity of the probe array can
be enhanced.
[0129] As a modification example of the probe-array substrate 100c
illustrated in FIG. 13, a probe-array substrate that does not
include the protrusive wall 118 providing the inspection region 106
and has a shorter distance between neighboring walls 116 can be
used. In this case, the size of the probe-array substrate can be
reduced.
[0130] While preferred embodiments of the invention have been
described above, it is to be understood that variations and
modifications will be apparent to those skilled in the art without
departing from the scope and spirit of the invention. The scope of
the invention, therefore, is to be determined solely by the
following claims.
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